A first rapid synoptic magnetic field map using SDO/HMI and SO/PHI data

Context. Traditionally, the observation time needed to build synoptic maps of the solar magnetic field is bound to the 27 days of a full Carrington rotation due to the single viewpoint from Earth. Aims. Our aim is to reduce this observation time to 13.5 days by combining magnetograms from two vantage points, 180◦ apart in longitude in the ideal case. Methods. We combined observations taken by the Polarimetric and Helioseismic Imager (SO/PHI) during the superior conjunction of the Solar Orbiter in February 2021 with data from the Helioseismic and Magnetic Imager (SDO/HMI) and constructed a synoptic map of the line-of-sight magnetic field of CR 2240. Resuls. The result is the first multi-view synoptic map using SDO/HMI and SO/PHI data from an observing period of only 16 days. Comparing the multi-view synoptic map to the standard synoptic map of SDO/HMI shows a significant amount of magnetic evolution between the dates on which the two instruments observed the same solar longitudes. The changed magnetic field was caught by the multi-view synoptic map but would have been missed by a standard synoptic map. Conclusions. Our results demonstrate that multi-view synoptic maps provide a new method to obtain a more instantaneous map of the magnetic field over the entire solar surface.